Field of the Invention
The invention relates to a head-up display apparatus including a combiner.
Description of the Background Art
Recently, head-up display (HUD) apparatuses that can display various information overlapped with objects in the field of view of a user have been commercialized. In the case of a HUD apparatus including a combiner, an image displayed by a displaying device is enlarged and reflected by the combiner, and then the image appears as a virtual image in front of the combiner.
When such a head-up display apparatus is mounted on a vehicle, such as a car, a driver can obtain the various information by seeing the displayed virtual image, keeping looking ahead during driving a vehicle without significant change in the line of sight.
If the combiner of such a head-up display is continuously exposed to direct sunlight and dust in the air, the exposure may accelerate deterioration of the combiner. Therefore, some proposed head-up display apparatuses include a combiner that is configured to be stored in a housing when the combiner is not used and to be uncovered outside the housing only while being used.
Moreover, recently, a higher resolution of an image displayed by the head-up display apparatus is requested. A vacuum fluorescent display (VFD), a liquid crystal display (LCD) or another type of display devices that represent images by a combination of light of a plurality of picture elements is generally used as a display device of the head-up display apparatus. However, in a case where such a display device is used for the head-up display apparatus, it is difficult to improve resolution of an image because light of each picture element is enlarged by the combiner.
One solution to this problem is use of a projector that represents images on a screen by emitting projection light. Projectors can display the images with relatively high resolution on a relatively small screen so that the resolution of the image can be improved. However, the projectors need a space serving as a path of the projection light from a lens that emits the projection light to the screen. Therefore, in a case where the projector is used for the head-up display apparatus, the apparatus may be bigger.
In a case where the head-up display apparatus is configured to store the foregoing combiner, a space serving as a path of projection light is required in the housing, in addition to spaces for the storage and move of the combiner. As a result, the head-up display apparatus may be even bigger.
On the other hand, in order to place the head-up display apparatus freely, it is better for the apparatus to be as small as possible. Thus, even in the case where the projector is used for the head-up display apparatus, a technology that makes the apparatus smaller is requested.